RGTT200K is a power reactor, designed based on HTGR tech-nology having capability to operate at high temperatures. RGTT200K features are 200 MWth power, helium-cooled, graphite moderator and reflector, pebble fuel type, and uses the Brayton direct cycle. Helium Inventory Control System (HICS) is one of its safety system which maintains the pressure, the helium coolant quality and quantity to meet safety requirements. The HICS consists of 3 subsys-tems, namely: Inventory Control System (ICS), Helium Purification System (HPS), and Helium Make-Up System (HMS). All of the systems have the function to maintain pressure, helium quality and quantity so that the reactor can operate reliable and safely. This paper discusses the performance of the ICS, which is integrated to the reactor coolant. The research objective was to determine the helium storage tank response rate, when primary coolant is overpressured and depressurized. The methodology used in this research is modeling and simulation by using ChemCAD. In previous re-search, the HPS, ICS and HMS have been modeled but have not been integrated yet in to the primary coolant. The simulation results showed that the time required for the injection tank back to the cool-ant normal pressure of 52 bars, due to depressurization up to 5 % was 160 seconds. While the time required for bleeding / blowdown to the storage tanks due to overpressurization up to 5 % was 186 seconds.

Research on the effect of the concentration of the inhibitor on the corrosion behavior of carbon-steel material has been done. The research was started by immersing the prepared carbon-steel plate in a 1 M HCl en-vironment. After that, corrosion inhibitor was added with several concentrations, which are 0, 100, 200, 300, and 400 ppm in to that environment, to be stirred using a magnetic stirrer at 300 rpm for 30 minutes under room temperatur condition. The effect of the added inhibitor was then analyzed using the Electrochemical Impedance Spectroscopies (EIS) method. The experiment results showed that the greater the concentration of the inhibitor, the greater the resistance, so that the metal is more pro-tected from corrosion attack. The calculation results showed that the inhibitor efficiency is directly proportional to the concentration of inhibitor that is achieved at a concentration of 400 ppm with an efficiency of 71.24%.

The G.A Siwabessy reactor (RSG-GAS) located in the Puspiptek area uses water as a coolant. The water as a coolant will contact directly with the component or structure of the reactor, that a chemical reac- tion between water and those components might cause the possibility of corrosion process. Therefore, cooling water quality will determine the integrity of reactor components or structures. The research described in this paper was conducted in order to monitor the quality of secondary cooling water, so that the water quality specifications is maintained and the reactor can be safely operated. One way to monitor the cooling water quality is by performing analysis into the secondary cooling water and raw water on June 6, 2016. The methodology used was by analysing the pH value using a pH-meter, conductivity value using Conductivity-meter, water hardness analysis, and analysis for some chemical elements such as Cl-, SO42-, Fe, P using calibrated Spectrophotometer DR / 2400. Corrosion rate of the carbon-steel as the piping material of secondary cooling system under environmental corrosion condition was also analyzed using the Potentiostat. From those performed analysis, the overall measured values are still below the standard values as required in the RSG-GAS safety analysis report document, meaning that the water quality management of the secondary coo- ling system has been well performed so far.Â

THE DEBRIS PARTICLES ANALYSIS OF RSG-GAS COOLANT TO ANTICIPATE SEDIMENT-INDUCED CORROSION. The reliability of the structures, systems and components (SSC) of the G.A. Siwabessy Multipurpose Research Reactor (RSG-GAS) should be maintained to keep the reactor operates safely. Chemical control and management of coolant is one factor which determines the SSCâs reliability. The debris sedimentation in the primary coolant system must be examined. Debris occurs in the reactor pool, originating from airborne dust from the engineering hall. Several elements contained by the sediment can induce corrosion. This research was conducted to identify the trace elements which were contained in the sediments and determine their concentrations. The objective was to anticipate the occurrence of galvanic and pitting corrosion due to the presence of elements which are more noble than aluminum. The measurement methodology is Neutron Activation Analysis (NAA). Two groups of samples were analyzed; the first group was sampled from the debris trapped in the mechanical filter after the resin column, or known as the resin trap, and second was sampled from the debris which adhered to the heat exchanger tube. The primary coolant debris analysis showed that the neutron-activated sediment contained Na-24, Na-25, Al-28, Mg-27, Cr-51, Mn-54, Mn-56, Co-58, Co-60, Ni-65, and Fe-59. The Mn, Cr, Co, Ni, and Fe are more noble than aluminum can induce galvanic corrosion while Na, Ba, Al, and Mg are not. The radionuclides contained by the result of neutron activation of sediment from the heat exchanger tube are Mn-56, Na-24, As-76, Br-82, Fe-59, Zn-65, Cr-51, La-140, and Sc-46 which are mostly carbon steel corrosion products. Those elements do not initiate galvanic corrosion. The prevention of galvanic corrosion can be done by periodic maintenance.Key Words : sediment, debris, corrosion, galvanic, pitting, RSG GasÂ Â